Date: Fri, 11 Apr 2008 08:34:29 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: gnn@freebsd.org Cc: current@freebsd.org Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <18431.23276.913397.188219@grasshopper.cs.duke.edu> In-Reply-To: <m2d4oy8n30.wl%gnn@neville-neil.com> References: <m2d4oy8n30.wl%gnn@neville-neil.com>
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gnn@freebsd.org writes: > Howdy, > > Is the TSC timecounter synchronized across multiple cores and/or > processors? A quick search seems to indicate it's not but I'd like to > find a definitive reference on the TSC. There is a great comment in the OpenSolaris source code talking about TSCs and their behavior on SMP systems. See http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/i86pc/os/timestamp.c FWIW, solaris manages to keep track of unsynchronized TSCs, and use unsynchronized TSC timecounters for timekeeping on SMP systems. It would be nice if FreeBSD could do the same. Drew
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